SR Street/Track Day Tire Comparison Test - Both Sides Of The Fence

Decipher The Codes
There are a lot of letters and numbers on a tire. Here is what the important ones mean:

Sometimes it seems as if there should be a codebook to understand all of the information on a tire's sidewall. Using a Dunlop D218 (an OEM variant of Dunlop's D208ZR Sportmax) as an example, this guide will help you know what to look for. The most important label is the sizing designation, which in this case reads "120/70ZR17." This indicates section width (120mm), aspect ratio (70 percent), speed rating (Z), construction (R) and wheel diameter (17 inches). This tire, as most sport tires do, has a speed rating of "Z" or more than 149 mph, and is a radial (R) construction. Following the size label is an additional marking defining the load rating for the tire. In this case, "58W" indicates the total load-carrying capacity is 520 pounds.

If you look at the accompanying chart in this test containing all the tire measurements, you'll note that not all tires are exactly the same size, even though their size designations are identical--one company's 120/70-17 tire will not be the exact same dimensions as another company's 120/70-17 tire. Everything from the sidewall height to the actual tread width to the circumference can vary wildly between manufacturers. This is important, especially if you're very close on clearance to the swingarm or other hard part on the motorcycle. Just as important is the fact that changing tires will likely change your bike's chassis attitude, which will affect handling because of the different circumferences as well as the dissimilar profiles.

Also molded into the sidewall is a DOT code, and the important part of this is the last four digits, indicating the week and year in which the tire was manufactured. In this case, 4104 indicates the tire was made in the 41st week of 2004. A tire's shelf life depends greatly on where and how it was stored, although most manufacturers agree that a tire loses its performance qualities after about four years. And finally, raised triangles at several places show where the tread wear indicators are located. There is still more information molded into the sidewall, but that is the most important data to consider when replacing tires.

The tire shown is the stock Dunlop D218 front tire from an '05 Honda CBR600RR. While the "F" denotes this as a front tire (typical of Dunlop's markings, but not all manufacturers'), the "K" after the size indicates the OEM variant. These model-specific tires are subtly modified from the standard units as requested by a specific manufacturer, whether for lighter weight, better mileage or even a slightly different tread pattern as with the D218. Some OEM tires are available through aftermarket retailers, or can be purchased from your dealer using the manufacturer's part number.

Also marked on the side of each tire is the number and type of plies in the tread and sidewall construction. For this D218, two nylon plies run across the tire from bead to bead (the sidewall plies), while the tread area has an additional two aramid plies. The OEM variant tires sometimes have a different belt package than the manufacturer's standard version, and often a slightly different compound as well. And in the case of multiple-compound tires, the OEM version is often altered as well; the OEM edition of the Bridgestone BT-016 on the Kawasaki ZX-10R, for example, only has two different compounds in its construction as opposed to the three different compounds used in the off-the-shelf model BT-016.